Electrical heating pad



June 17, 11941. W, BRADFQRD 2,246,238

ELECTRICAL HEATING PAD Filed June 30, 1959 2 Sheets-Sheet l lNVENTOR WILL/4M BRADFORD JUN? 11? 1941. W BRADFORD 2,24%,238

ELECTRI CAL HEATING PAD Filed June 50, 1939 2 Sheets-Sheet 2 INVENTOR WILL/AM BRADFORD CAQfW/V W ATTORN YS Patented June 17, 1941 UNITED STATES PATENT OFFICE 2,248,238 ELECTRICAL HEATING PAD William Bradford, Taunton, Mass. Application June 30, 1939, Serial No. 282,121

This invention relates to improvements in elec trical heating pads, and is directed in particular to the design of an improved pad which is capable of being used in an improved manner somewhat in the same way as a kidney plaster, or alternatively may be folded up so that it may be used as a smaller pad for local application.

One object of the invention is to produce a pad of this character which may be used over the kidney area whilethe patient is lying either flat on his back or on one side without danger oil overheating the pad in any of these condit one.

A further object is to ment construction which be folded transversely in of smaller compass.

A Iurther object is to produce a pad of this general character in which there is no danger of overheating in the central portion or the pad even though the thermostat controls are placed at a considerable distance from it.

A further object is to produce a pad of this general character in which the temperature oi either side may be regulated as desired, while preserving a safety control by means of a high temperature limit thermostat in th other half of the pad.

Other and further objects of the invention will appear from the following description and claims.

Referring to the drawings:

Fig. 1 is a plan view of a pad constructed in accordance with the invention, certain parts being broken away in order to disclose the connections;

Figs. 2, 3, 4 and 5 are details illustrating different positions of the regulating switch:

Fig. 6is-a diagram showing a difierent type of circuit having somewhat difierent functions; and

Fig. 7 is a detail of a modification of Fig. 1.

Referring first to the form of device shown in Figs. 1 to 5, the pad is constructed of a backing l0 having resistance elements ll coiled in each half of the pad. It will be observed that the general nature of the pad is such as to provide a relatively narrow central portion l2 and two larger end portions or lobes it. In accordance with one aspect of the invention the heating elements have a substantially greater concentration in the two enlarged side portions l3 so that there will be no danger or overheating the central portion and no necessity of providing the central portion with a thermostatic control.

provide a heating elewill permit the pad to order to form a pad at the right forms tons 21 and It should further be observed that this type of pad is susceptible to temperature variations of considerable magnitude between one side and the other. For example, if the pad be placed across the small of the back, and the patient be upon one side, it may easily result that the side of the heating pad underneath the patient is thoroughly" protected against radiation loss, while the other side is freely exposed to the air. To prevent overheating of one side under these conditions We thermostats i4 and I! are used, placed respectively in the opposite lobes of the pad. The thermostat I4 is connected by a wire I to the looped central portion of the wire I I. This looped wire is wound spirally as shown. and its ends are connected by bridge wires I! as in Fig. 1 or by continuations of the resistance wires themselves as in Fig. '7 to similar looped wires II in the other lobe.

It will be seen that the wire in the lobe shown coils 20 and?! of resistance wire joined by bridge wires II to resistance wire coils 22 and 23 in the other lobe. The end 0! the thermostat I4 is not connected with the wire It but is joined to the second thermostat It by a wire 24 and the other end oi'the thermostat ii is joined by a wire 25 with one side of the line. The other side of the line leads to .a switch blade 26 (Figs. 2 to 5) adapted to make contact with buttons 2'! and 28, in the manner shown in the various figures. The switch button 21 is connected to the resistance wire 22: the button 28 to the resistance 23. i

Fig. 2 shows the position of the circuit with the switch in "ofl position.' In Fig. 3 the switch is connected to the button 21 and current flows through the coils 20 and 221only, returning to the line through the thermostats and IS in series. The coils 20 and 22 are so chosen as to give a low heat. In Fig. 4 the switch blade is connected with the button 28 only, current in this case passing through the resistance coils 2i and 23 which are chosen so as to give a medium heat. In Fig. 5

28 and the current flows in parallel through the two circuits previously described, increasing the heating rate.

It will be observed that'in each case'there is a limit control thermostat in each lobe oithe pad in series with one side of the line so'that, irrespective of the conditions of one half'oi the pad with respect to free radiation, overheating of the other side will cause the circuit to be opened.

In Fig. 6 has been shown a modification of the the switch blade bridges butcircuit embodying two identical resistance coils 33 and 3| in the two lobes of the pad. In each lobe is mounted a high and low combination thermostat 32 each with a central tap, the two taps being provided with a short circuiting switch connection 33. There are in this case two switches, a short circuiting switch 33 and the lin opening switch 34, which may be combined if desired. The double thermostat in this case may be of the type shown and claimed in my copending application Serial No. 271,076, May 1, 1939. This form of the invention, whil producing only two heats, has the advantage that the control is more positive on the low heat than it i in the type previously discussed. For example, it will be seen that there is a low heat thermostat L in each lobe of the pad, this being in series with the circiut when the switch 33 is open. If either-lobe becomes higher in temperature than that for'which these thermostats are set, the corresponding low temperature thermostats will be opened'and the entire circuit through both lobes broken. The high temperature-thermotsats H meanwhile remain also in series with the circuit and serve as safeguards in case of a short circuit which might cause rapid heating of one side of the pad. These high temperature thermostats also assume complete control of the circuit when the switch 33 is closed, thus short circuiting the two low temperature thermostats.

The pad as described above in connection with Fig. l is of novel construction in that it consists of two mutually connected heating circuits, one in each lobe, with no heating element in the narrowed section between the lobes and the two resistance units connected by flexible wires. Due to this feature, this form of pad has an additional utility in that it may be readily folded in half and used as a small round pad which can be applied on a smaller surface, such as the jaw.

What I claim is:

1. An electrical heating pad having two lobes separated by a relatively narrow neck, each lobe comprising an electric heating element, the two elements being connected in series with the line and with each other, a combination high and low temperature thermostat located in each lobe, each thermostat having its high terminal connected to the heating element and having its low terminal connected to the low terminal of the other thermostat, and a circuit including a switch for short circuiting the low temperature thermostats.

2. A heating pad formed in a pair of sections foldable one upon another upon an intermediate fold line, each section comprising a substantially circular lobe with the sections connected to-,

gether by a neck portion narrowed at the fold line of the two sections and forming a pad resemblingin shape a kidney .plaster, mutually connected heating circuits for the two sections, each heating-circuit comprising a pair of heating coils formed of a pair of wires of different resistance rranged in two mutually interjacent concentric spirals, common input wires for the two circuits joined to the pad at a point remote from the intermediate fold line, and a pair of serially connected thermostats one in each lobe connected at one end to one of said common input wires and at the other end to said heating circuits.

aseassa 3. A heating pad comprising two symmetrical substantially circular lobes connected by a relatively constricted neck forming a fold line, whereby the pad may be used in unfolded condition for use in applying heat as to the back or chest, or may be folded along the fold line with the lobes in superposed relation to form a small substantially circular heating pad for use as on the Jaw or ear, individual heating circuits in each of the two sections mutually and flexibly connected across the neck of the pad. common input wires for the two circuits joined to the-pad at a point remote from the common fold line, and a plurality of similar thermostats located one in each pad andconnected to said heating circuits to interrupt energization of the heating circuits whenever the temperature in either lobe exceeds a predetermined maximum.

4. A heating pad comprising two symmetrical substantially circular lobes connected by a relatively constricted neck forming a fold line, whereby the pad may be used in unfolded condition for use in applying heat as tothe back or chest, or may be folded along the fold line with the lobes in superposed relation to form a small substantially circular heating pad for use on the jaw or ear, a pair of individual heating circuits, each extending through both of the two lobes, each circuit being formed with a discrete concentration of heating elements in each lobe flexibly connected together across the neck of the pad, a pair of input wires one extending from the end of each circuit in one lobe and extending outwardly from the pad at a point of said'lobe remote from the common fold line, a common thermostat circuit comprising a wire extending outwardly from said lobe at said point, extending through said lobe into the remote lobe, and being connected in said remote lobe to those ends of the two heating circuits remote from the connection across the neck, a pair of thermostats connected in the thermostat circuit, one being located in each lobe, and a switch for connecting the heating circuits selectively to a source of electrical power.

5. A heating pad comprising two symmetrical substantially circular lobes connected by a relatively constricted neck forming a fold line, whereby the pad may be used in unfolded condition for us for applying heat as to the back or chest, or may be folded along the fold line with the lobes in superposed relation to form a small substantially circular heating pad for use as on the jaw or ear, individual heating circuits in each of the two lobes mutually and flexibly connected across the neck of the pad, an input wire for said circuits connected to the heating circuit in one lobe and extending outwardly from the pad at a point of said lobe remote from the fold line, a thermostat circuit comprising a wire extending outwardly from said lobe at said point, extending through said lobe into th remote lobe, and being connected therein to that end of the heating circuit remote from the connection across the neck, and a pair of thermostats connected in said thermostat circuit, one of said thermostats being located in each lobe.

WILLIAM BRADFORD. 

